1. Field of the Invention
The present invention relates to an inkjet recording apparatus and, more particularly, to an inkjet recording apparatus provided with a conveying belt for conveying a recording medium.
2. Description of the Related Art.
In recent years, an inkjet recording apparatus is widely used as an apparatus for forming images on various recording mediums. Such inkjet recording apparatus uses a plurality of nozzles to discharge ink onto a recording medium conveyed to a position facing the nozzles so that an image is formed on a recording medium. Therefore, an inkjet recording apparatus is advantageous in that it is small and inexpensive, is quiet during operation, and is capable of forming a fine image.
In such inkjet recording apparatus, a method of using a conveying belt may be adopted as a method for conveying a recording medium to a nozzle-facing position. According to this method, a recording medium is supported on a surface of a conveying belt and conveyed to the nozzle-facing position, and an image is formed on the recording medium while the recording medium is supported on the surface of the conveying belt. At this time, ink discharged from the nozzle may adhere to the conveying belt. For example, in the case where a recording medium is made of material such as fabric which may allow ink to pass therethrough, ink may pass through the recording medium and adhere to the conveying belt. Further, even in the case where the recording medium is made of a recording sheet which is not likely to allow ink to pass therethrough, if an image is formed on a whole area of the recording sheet without providing a space on edge, ink may adhere to the surface of the conveying belt in an area beyond outer edge of the recording medium. When a recording medium following the previous recording sheet is supported on the conveying belt to which ink adheres, it causes a problem that a back surface of the following recording medium may be contaminated.
Therefore, in an inkjet recording apparatus provided with a conveying belt, a cleaning section for cleaning a surface of the conveying belt to remove ink adhered to the surface of the conveying belt. As a configuration of such cleaning section, there has been a known configuration of providing a cleaning roller which comes in contact with a conveying belt on a downstream side of a position where a recording medium is separated apart from the conveying belt (for example, refer to Japanese Patent Publication No. 2005-212276). A part of the cleaning roller is soaked in cleaning liquid stored in a container. According to this configuration, a cleaning roller rotates with movement of the conveying belt in a state of being in contact with the conveying belt, so that ink adhered to the surface of the conveying belt is removed. Further, ink adhered to the cleaning roller is separated from the cleaning roller and disperses in cleaning liquid when the cleaning roller is in a state of being soaked in cleaning liquid stored in the container.
In the cleaning section having such configuration as described above, amount of ink in cleaning liquid stored in the container gradually increases as cleaning of the conveying belt is repeatedly performed. When the amount of ink in cleaning liquid becomes great, it gradually becomes difficult to remove ink from the cleaning roller. In this case, ink adhered to the conveying belt becomes also difficult to be removed. Further, when the cleaning roller is soaked in cleaning liquid stored in the container, ink in cleaning liquid adheres to the cleaning roller, so that ink adhered to the cleaning roller is likely to adhere to the conveying belt. Therefore, cleaning liquid stored in the container is replaced with new cleaning liquid as needed.
Such replacement of cleaning liquid is performed automatically, for example, when a length of movement of the conveying belt in contact with the cleaning roller reaches a prescribed length, or when a time length of movement of the conveying belt in contact with the cleaning roller reaches a prescribed time length. However, the amount of ink adhered to conveying belt varies depending on an image recording condition. Therefore, in a control of replacing cleaning liquid at a time of reaching the prescribed length or prescribed time length, it may cause a situation where cleaning liquid still having sufficient cleaning ability is replaced and a situation where cleaning liquid including a large amount of ink is not replaced. In summary, it may cause a situation where cleaning liquid is wastefully lost and a situation where the conveying belt cannot be cleaned sufficiently.
As a countermeasure to this, Japanese Patent Unexamined Publication No. 2005-212276 discloses a technology of changing a supply rate of cleaning liquid in accordance with an image recording condition such as a kind of recording medium, size of image, and amount of use of ink. This document indicates that a cleaning belt can be cleaned efficiently and sufficiently by adopting the disclosed technology.
With the technology disclosed in the document, the conveying belt can be adequately cleaned as long as a recording medium of a kind which is set is normally conveyed. However, in an actual inkjet recording apparatus, abnormality in conveyance of recording medium may sometimes occur. For example, there are cases where a recording medium jams during conveyance and where a recording sheet is conveyed in a state where it has deformation such as ripping and bending, and curling. In such cases, the recording medium is not at its proper position on the conveying belt, so that ink is discharged directly onto the surface of the conveying belt. Further, a user may mistakenly supply a recording medium which is different from a recording medium of a kind which is set. In this case, the amount of ink adhered to the conveying belt may be different from the amount which supposed to be in the case where the recording medium of a kind which is set is conveyed. In other words, it may cause at least a situation where the conveying belt is contaminated more than expected, or a situation where the conveying belt is not contaminated as expected.
As described above, it would be difficult to estimate contamination of cleaning liquid only in accordance with an image recording condition. Therefore, the technology disclosed in the document has a problem that it may cause at least a situation where cleaning liquid having sufficient cleaning ability is replaced, or a situation where cleaning liquid including a large amount of ink is not replaced.